Swine Herds Research Articles

Dynamics and chronology of Mycoplasma hyopneumoniae strain 232 infection in experimentally inoculated swine

Direct detection of Mycoplasma hyopneumoniae through molecular tools is a growing trend for early diagnosis, highlighting the importance of knowing M. hyopneumoniae dynamics in the respiratory tract upon infection. This study focused on monitoring the infection level and its effects in different anatomic sites of the respiratory tract of experimentally infected swine in four time-points post-infection. To this end, 24 pigs were allocated to either non-inoculated group (n = 8) or inoculated group (n = 16). On day 0 post-infection (dpi), animals of the inoculated group were intratracheally inoculated with M. hyopneumoniae. Nasal swabs were collected weekly for qPCR detection of bacterial shedding. At 14, 28, 42, and 56 dpi, four animals from the inoculated group and two from the control group were necropsied. Bronchoalveolar lavage fluid (BALF) and samples from three different anatomical tracheal sections (cranial - CT, medium - MT, lower - LT) were collected for qPCR and histopathology. Bacterial loads (qPCR) in tracheal samples were: 4.47 × 102 copies∕μL (CT), 1.5 × 104- copies∕ μL (MT) and 1.4 × 104 copies∕μL (LT samples). M. hyopneumoniae quantification in BALF showed the highest load at 28 dpi (2.0 × 106 copies∕ μL). Microscopic lesions in LT samples presented the highest scores at 56 dpi and were significantly correlated with the pathogen load on 14 dpi (0.93) and 28 dpi (0.75). The greatest bacterial load of M. hyopneumoniae in CT samples and BALF was registered at 28 dpi, and it remained high in BALF and LT throughout the 56 dpi. The pathogen was able to persist during the whole experimental period, however higher estimated quantification values were registered in the lower parts of the respiratory tract, especially at 56 dpi. These findings are important for improving diagnostics, treatment, and control measures of M. hyopneumoniae infection in swine herds.

First investigation on the presence of porcine parvovirus type 3 in domestic pig farms without reproductive failure in the Democratic Republic of Congo

Porcine Parvovirus (PPV) is one of the major pathogens responsible for reproductive failure in sows. However, the information on its frequency in the Democratic Republic of Congo (DRC) is largely unknown. Thus, the present study was carried out to detect and genetically characterize some of known Parvovirus namely porcine parvovirus 1, 2, 3, 4, porcine bocavirus (PBoV) 1, and porcine bocavirus-like virus (PBolikeV) in 80 randomly selected archive pig farm samples during an African swine fever (ASF) survey in South Kivu, eastern DRC by polymerase chain reaction (PCR). The majority of animals analyzed (82.5%) were local breeds, and most of them (87.5%) were adults (above one year old). The majority of the animals (65%) were from the free range farms. The PCR result indicated that only PPV3 was detected in 14/80 pigs. Seven swine herds (8.7%) were co-infected with PPV3 and ASFV. Morever, a significantly high PPV3 infection rate was observed in the spleen (66.7%, P<0.0001) compared to the others type of samples. Further, the phylogenetic analysis of partial PPV3 sequences revealed one clade of PPV3 clustered with PPV3 isolates reported in a previous study in Cameroun, China, Slovakia, Germany, and China. This study is the first to report the detection of PPV in DRC. Further studies are needed to assess the levels of PPV3 viremia and the impact in co-infections with other endemic pig viruses, including ASFV.

CRISPR/Cas9-based generation of a recombinant double-reporter pseudorabies virus and its characterization in vitro and in vivo

Pseudorabies, caused by pseudorabies virus (PRV) variants, has broken out among commercial PRV vaccine-immunized swine herds and resulted in major economic losses to the pig industry in China since late 2011. However, the mechanism of virulence enhancement of variant PRV is currently unclear. Here, a recombinant PRV (rPRV HN1201-EGFP-Luc) with stable expression of enhanced green fluorescent protein (EGFP) and firefly luciferase as a double reporter virus was constructed on the basis of the PRV variant HN1201 through CRISPR/Cas9 gene-editing technology coupled with two sgRNAs. The biological characteristics of the recombinant virus and its lethality to mice were similar to those of the parental strain and displayed a stable viral titre and luciferase activity through 20 passages. Moreover, bioluminescence signals were detected in mice at 12 h after rPRV HN1201-EGFP-Luc infection. Using the double reporter PRV, we also found that 25-hydroxycholesterol had a significant inhibitory effect on PRV both in vivo and in vitro. These results suggested that the double reporter PRV based on PRV variant HN1201 should be an excellent tool for basic virology studies and evaluating antiviral agents.

Development of a quantitative real time RT-PCR assay for sensitive and rapid detection of emerging Atypical Porcine Pestivirus associated with congenital tremor in pigs

Atypical Porcine Pestivirus (APPV) is reported as the etiologic agent for type AII congenital tremors in newborn piglets. Initial PCR-based diagnostic tests to detect APPV were designed based on the limited sequence information and are not capable of detecting the majority of APPV strains. A sensitive and reliable PCR-based diagnostic test is critical for accurate detection of APPV. In this study, a quantitative reverse transcription PCR (RT-qPCR) assay was developed for reliable detection of all currently known APPV strains. The assay design also included swine 18S rRNA gene as an internal control to monitor RNA extraction efficiency. Two APPV gene fragments, one each from NS5b and NS3, were cloned and used to determine the dynamic range of detection, linearity and analytical sensitivity/limit of detection (LOD). Both individual and multiplex assays (duplex and triplex) had correlation coefficients of >0.99 and PCR amplification efficiencies of >90 %. Comparison of detection limit and analytical sensitivity between individual, and multiplex assays indicated no inhibition of PCR sensitivity upon multiplexing. The detection limit for APPV target, based on analytical sensitivity, is 7.75 copies (NS5b) and 5.2 copies (NS3) per reaction. Assay specificity was verified by testing nucleic acids of other closely related pestiviruses and clinical samples that are positive for other common swine pathogens. Assay sensitivity was also assessed on synthesized gene fragments of the most divergent China strains. Testing 339 known APPV-positive and 202 negative clinical samples demonstrated a good diagnostic sensitivity and specificity. Data from six independent runs, including 5 replicates of three clinical samples with three Ct ranges, were utilized to assess inter-assay repeatability and intra-assay reproducibility. This analysis demonstrated intra-assay/inter-assay coefficients of variation of 0.71 % and 0.01 %, respectively, with a PCR efficiency of 92.71 % for the triplex assay. Testing of 1785 clinical samples revealed ∼19 % prevalence of APPV in the US swine herds and oral fluids demonstrates to be a reliable specimen for viral detection. This multiplex RT-qPCR assay offers a rapid and reliable detection of APPV in swine herds and serves as useful tool in APPV surveillance and epidemiological investigations.

Swine Production and Challenges in Vietnam after African Swine Fever: A Case Study in Peri-Urban Hanoi, Vietnam

The goal of this paper was to identify major challenges in rebuilding the swine industry in Vietnam, using the Chuong My district, Hanoi as a case study. Primary data was gathered in 2020 mainly through a survey of 97 swine producers in the district. Analysis tools were descriptive and comparative statistics. Results show that after the ASF outbreak, the recovery of the swine industry in Vietnam faced several challenges, including the issues of piglet quantity and quality, changing consumer preferences which were worsened by the current Covid-19 pandemic, relatively cost disadvantage of domestic production under the context of new free trade agreements, disease risk (ASF under the condition of no effective and safe vaccine), insufficient resources of farms to restock, and environmental issues caused by swine production in rural areas. The paper proposed several recommendations to rebuilding the swine herd in order to address the issues and overcome the challenges, mainly focus on improving sow quality, market information and linkages, good practices in production, training for labor, and address environmental issues.

Functional study of a role of N-terminal HA stem region of swine influenza A virus in virus replication

Swine influenza A virus (SIV) is both a pathogen of economic significance to the swine industry and a potential zoonotic organism that may be transmitted to humans. We described here the detailed characterization of a role of N-terminal B-loop and CD helix of HA2 in swine influenza A virus replication. Results of our experiments demonstrated that Hemagglutinin (HA) protein of swine influenza virus could tolerate some mutations in functionally conserved B-loop and CD helix. These mutations, however, have substantially attenuated influenza virus replication in both cell lines and porcine primary tracheal epithelial cells. Significantly, we found that some B-loop or CD helix mutations generated virus mutants that replicated in MDCK and ST cell lines but failed to replicate in primary tracheal epithelial cells, thereby suggesting that swine HA protein may function as a viral virulence and pathogenesis factor. The described mutations may be further explored as attenuated vaccine candidates that can effectively prevent or eliminate the spread of influenza virus within and between swine herds.

Global Distribution and Genetic Heterogeneity of Border Disease Virus.

Border disease virus (BDV) belongs to the genus Pestivirus of the family Flaviviridae. Interspecies transmission of BDV between sheep, cattle, and pigs occurs regularly, sometimes making diagnosis a challenge. BDV can yield substantial economic losses, including prenatal and postnatal infections in lambs, which are the primary source of infection and maintenance of the virus in the population. Since BDV is antigenically and genetically related to bovine viral diarrhea virus (BVDV), it might pose a significant risk to cattle, influencing BVDV eradication campaigns. Similarly, the presence of BDV in swine herds due to pestivirus spillover between small ruminants and pigs might cause uncertainty in classical swine fever virus (CSFV) diagnostics. Therefore, knowledge of BDV epidemiology in different geographical regions will help prevent its spread and optimize control measures. Previous epidemiological studies have shown that various BDV genotypes are predominant in different countries. This review provides an overview of the spread of BDV world-wide in different host species.

11 Metal Amino Acid Chelates/complexes with Emphasis on Molecule Absorption and Efficacy Differences in Swine

Abstract The objective of this presentation will be to discuss differences in the molecular structures between various organic trace minerals (OTM) and inorganic trace minerals (ITM) and discuss how these properties impact stability, absorption, bioavailability and retention. The Association of American Feed Control Officials (AAFCO) lists several different categories of OTM including chelates, complexes and proteinates. Typical ligands include organic acids, amino acids, peptides and polysaccharides. It is widely known that bioavailability of ITM is low, primarily due to the presence of antagonisms such as phytate and/or fiber or excesses of other minerals. For this reason, inclusions of trace minerals (e.g. Zn, Cu, Mn, Fe) are often added in commercial livestock diets at 2–3-fold higher concentrations than recommended by NRC. Feeding highly bioavailable trace minerals is important. These minerals are required components of thousands of the proteins, enzymes and transcription factors that support a wide variety of biochemical processes in the cells and tissues of animals. These functions include gene regulation, cell growth and division, immune development and function, tissue development and integrity, reproduction and oxidative stress management. Low bioavailability of these trace minerals can reduce animal performance, immune function, reproductive performance and increase lameness. Numerous in vitro and in vivo methodologies have been used to compare bioavailability and demonstrate higher stability, tissue retention and digestibility of OTM vs ITM. Sow longevity is a key factor in commercial swine herd profitability. Reproductive problems and lameness are the most common reasons for premature sow culling from breeding herds. Compared to ITM, OTM reduced gilt and sow mortality 9–17% (P &amp;lt; 0.10), culling rate 20–35% (P &amp;lt; 0.01) and increased sow retention (through parity 3) 5–10%; (P &amp;lt; 0.01). Greater bioavailability translates to biological benefits to the producer, however, our findings demonstrate that not all OTM perform better than ITM.

14 Opening the Black Box of Fertility Prediction

Abstract Analysis of the U.S. swine herd shows variation in pregnancy rate is more attributable to male-factor subfertility than the dam. To date, a limited degree of correlations has been observed between conventional semen analysis parameters and actual fertility after standard quality cutoffs are met. Thus, a clear ability to predict male-factor fertility is lacking. Knowledge of what makes fertilization competent spermatozoa has been long sought after for centuries. It was only in the last half-century that we understood spermatozoa undergo a biological process after ejaculation to acquire the capacity to fertilize. Since then, work has been done to elucidate the molecular pathways involved in sperm capacitation. Recent technological advances in flow cytometry, namely image-based flow cytometry, allows for high-throughput, single-cell phenotyping. Single-cell phenotyping with biomarkers reflecting significant sperm capacitation events, mitochondrial status, cell health, and more, allows multi-million bioimage data sets to be easily attained. These datasets can then be analyzed utilizing machine and deep learning analytic methods and correlated with single sire field fertility data to open the black box of boar fertility prediction. Our findings establish a new paradigm in sperm function and pave the way for accurate fertility prediction in future precision agriculture applications. This work was supported by the National Institute of Food and Agriculture (NIFA), U.S. Department of Agriculture (USDA) award number 2019-67012-29714.

Classical, Molecular, and Genomic Cytogenetics of the Pig, a Clinical Perspective.

Simple SummaryChromosome rearrangements are one of the main etiological factors leading to impaired fertility in the domestic pig. The high prevalence of chromosome rearrangements in swine herds, coupled with the production of significantly lower litter sizes, has led to the implementation of cytogenetics techniques in screening prospective breeding boars for rearrangements. Beginning in the 1960s, classical cytogenetics techniques have been applied in laboratories, resulting in the identification of over 200 distinct chromosome rearrangements in the pig. More recently advances in technology, and the development of molecular cytogenetics and cytogenomics techniques, have enhanced the resolution of rearrangements and advanced diagnostic techniques, allowing for more precise and rapid diagnosis of rearrangements.The chromosomes of the domestic pig (Sus scrofa domesticus) are known to be prone to reciprocal chromosome translocations and other balanced chromosome rearrangements with concomitant fertility impairment of carriers. In response to the remarkable prevalence of chromosome rearrangements in swine herds, clinical cytogenetics laboratories have been established in several countries in order to screen young boars for chromosome rearrangements prior to service. At present, clinical cytogenetics laboratories typically apply classical cytogenetics techniques such as giemsa-trypsin (GTG)-banding to produce high-quality karyotypes and reveal large-scale chromosome ectopic exchanges. Further refinements to clinical cytogenetics practices have led to the implementation of molecular cytogenetics techniques such as fluorescent in-situ hybridization (FISH), allowing for rearrangements to be visualized and breakpoints refined using fluorescently labelled painting probes. The next-generation of clinical cytogenetics include the implementation of DNA microarrays, and next-generation sequencing (NGS) technologies such as DNA sequencing to better explore tentative genome architecture changes. The implementation of these cytogenomics techniques allow the genomes of rearrangement carriers to be deciphered at the highest resolution, allowing rearrangements to be detected; breakpoints to be delineated; and, most importantly, potential gene implications of those chromosome rearrangements to be interrogated. Clinical cytogenetics has become an integral tool in the livestock industry, identifying rearrangements and allowing breeders to make informed breeding decisions.

Antimicrobial Use in Brazilian Swine Herds: Assessment of Use and Reduction Examples.

Brazil, as a major pig producer, is currently experiencing the widespread use of antimicrobials as a serious issue to be addressed. For measures to be taken in this direction, the extent of the problem must be known. The goal of this study was to evaluate the use of antimicrobials in 25 Brazilian swine herds. Antimicrobial use from birth to slaughter was correlated with biosecurity and productivity. After the first assessment (2016; M0), 13 herds implemented good practices to reduce antimicrobial use. Four years after the implementation of these measures (2020; M1), data about antimicrobial usage from these herds were collected. The results of the first assessment (M0) demonstrated a troublesome scenario: the mean value of antimicrobials used was 358.4 mg/kg of pig produced; the median of the pig’s lifetime exposure to antimicrobials was 73.7%, and the median number of drugs used was seven. A positive correlation between the antimicrobials consumed and the pig’s antimicrobial exposure time was detected. Nevertheless, these data did not correlate with biosecurity score or productivity. A significant difference was detected in M1, where a median 30% reduction in antimicrobials consumed was detected. There was also a 44.3% reduction of the pig’s lifetime exposure to antimicrobials. The median number of drugs used was reduced from seven to five. Antimicrobial use did not always reflect the sanitary condition or the real therapeutic needs, easily leading to overuse.

Recombinant pseudorabies virus with gI/gE deletion generated by overlapping polymerase chain reaction and homologous recombination technology induces protection against the PRV variant PRV-GD2013

BackgroundSince 2011, numerous highly virulent and antigenic variant viral strains have been reported in pigs that were vaccinated against the swine pseudorabies virus. These infections have led to substantial economic losses in the Chinese swine industry.ResultsThis study, constructed a novel recombinant vaccine strain with gI/gE deletion (PRV-GD2013-ΔgI/gE) by overlapping PCR and homologous recombination technology. The growth curves and plaque morphology of the recombinant virus were similar to those of the parental strain. However, PRV-GD2013-ΔgI/gE infection was significantly attenuated in mice compared with that of PRV-GD2013. Two-week-old piglets had normal rectal temperatures and displayed no clinical symptoms after being inoculated with 105 TCID50 PRV-GD2013-ΔgI/gE, indicating that the recombinant virus was avirulent in piglets. Piglets were immunized with different doses of PRV-GD2013-ΔgI/gE, or a single dose of Bartha-K61 or DMEM, and infected with PRV-GD2013 at 14 days post-vaccination. Piglets given high doses of PRV-GD2013-ΔgI/gE showed no obvious clinical symptoms, and their antibody levels were higher than those of other groups, indicating that the piglets were completely protected from PRV-GD2013.ConclusionsThe PRV-GD2013-ΔgI/gE vaccine strain could be effective for immunizing Chinese swine herds against the pseudorabies virus (PRV) strain.

DETECTION OF SAPOVIRUS IN BRAZILIAN PIG FARMS

Sapoviruses (Caliciviridae) are considered important gastroenteritis worldwide affecting animals and humans. In pig farming, the epidemiology has not completely understood, because can affect all stages of production, with symptomatic (diarrhea) or asymptomatic pigs. The aim of our study was investigated Sapovirus occurrence in Brazilian pig farms. A total of 166 fecal samples of pigs, with different ages, from Minas Gerais, São Paulo and Mato Grosso States were submitted to RT-PCR reactions and confirmed with nucleotide sequencing of Sapovirus RdRp gene. In total, six (3.61%) samples were positive and four of them had partial RdRp gene sequenced, putatively belonging to GVII.1 genogroup, also previously reported in swine herds in Brazil.

Determination of hardness and mechanical properties of pig claws in three Greek swine herds

Lameness in pigs is a major welfare and economic issue for swine breeding herds. Claw lesions have been suggested to be a significant cause for lameness in sows. Housing conditions and nutrition management on the farm influence horn quality and may be associated with the development of claw lesions in pigs. The current work examines the structure as well as hardness, fracture and mechanical properties of claws retrieved from housing sows. For the mechanical characterisation of pig claws, an experimental program that includes three point bending test in claws was performed in order to obtain the resistance of the tissue under bending forces. The study also includes hardness measurements through Vickers method as well as inspection of the structure through Scanning Electron Microscopy. Experimental measurements show that the claw specimen behaves as a linear viscoelastic material. Measurements of hardness were found to be affected by the moisture content of the claws.

Determination of hardness and mechanical properties of pig claws in three Greek swine herds

Determination of hardness and mechanical properties of pig claws in three Greek swine herds

A retrospective study of porcine reproductive and respiratory syndrome virus infection in Brazilian pigs from 2008 to 2020.

Porcine reproductive and respiratory syndrome (PRRS) is a viral disease characterized by reproductive impairment or failure in breeding animals, and a respiratory disease in pigs of any age. Brazil is the fourth largest pork producer and exporter globally, and PRRS virus (PRRSV) infection has never been reported in the country. This study aimed to investigate the status of porcine biological samples from commercial swine herds, quarantined imported boars, wild boars and feral pigs to update PRRS information in Brazil. A total of 14,382 samples were collected from 2008 to 2020, including sera (n=12,841), plasma (n=1,000) and oral fluids (n=541), comprehending 137 herds and free-living pigs in eight Brazilian states. One out of 1,000 (0.1%) plasma and 15 out of 12,841 (0.11%) serum samples tested positive for PRRSV antibodies through ELISA. Upon ELISA retesting, only the plasma sample, from one 8-day-old piglet remained positive. All sixteen previously PRRSV antibody-positive samples were tested through RT-PCR and found to be negative. The presence of false-positive or singleton reactors are quite expected. Thus, the use of different/alternative diagnostic tests is indicated for an efficient PRRSV detection. Taken together, our findings demonstrated no conclusive evidence of PRRSV infection in the tested pigs, highlighting the importance to reinforce the surveillance program to prevent the introduction and eventual dissemination of PRRSV in Brazil.

A novel spike subunit 1-based enzyme-linked immunosorbent assay reveals widespread porcine torovirus infection in eastern China.

Toroviruses (ToVs), closely related but genetically distinct from coronaviruses, are known to infect horses, cows, pigs, goats and humans, mainly causing enteritic disorders. However, due to the lack of an adaptive culture system, porcine ToV (PToV) has received less attention. In this study, we developed a novel serological detection method based on the PToV envelope spike subunit 1 (S1) protein for the first time, and compared it to an existing indirect enzyme-linked immunosorbent assay (ELISA) based on the nucleocapsid protein. By using the S1-based ELISA, we carried out the first seroepidemiological survey of PToV in China, assaying both specific IgG and IgA responses in 1,037 serum samples collected from diarrheic pigs in eastern China. There was a relatively high incidence of seropositivity in pigs of different ages, especially one-week-old piglets and sows (78% and 43%), the former probably reflecting maternal antibodies. Furthermore, 3/20 (15%) of faecal samples collected from one PToV-seropositive swine herd in Zhejiang province tested positive by RT-PCR. The complete PToV genome was sequenced from one of these samples, and its phylogenetic relationship with other full-length PToV sequences available in GenBank was determined. Our data provide the first serological evidence for PToV infection in pigs from China, which will help elucidate the potential pathogenicity of PToV in pigs.

Genetic diversity and prevalence of Atypical Porcine Pestivirus in the Midwest of US swine herds during 2016-2018.

Atypical porcine pestivirus (APPV), a highly divergent pestivirus, has a wide geographical distribution around the world. APPV is known to cause type A-II congenital tremors in newborn piglets. The main objective of this study is to access APPV prevalence in the US swine herds utilizing a newly developed quantitative real-time RT-PCR assay. Retrospective analysis of 1,785 samples revealed a 19.0% prevalence in Midwest swine herds over a period of three years (2016-2018). Among all clinical and field samples that were APPV positive, 82 samples (24.19%) were also positive for one or more swine viral pathogens. Two APPV US strains identified in this study demonstrated significant sequence diversity (~12% in full genome) compared to the first reported APPV strain from the United States in 2014. Of the two strains identified in this study, USA/023005/2016 is closer to two strains identified in Germany, and USA/047310/2017 shares more similarities with two US strains including Minnesota-1 and ISDVDL2014016573. Partial NS5B sequences (9127-9836 nt of the polyprotein gene) obtained from 54 APPV-positive samples revealed considerable sequence diversity, ranging from 85.8% to 100% nucleotide identity, within the US strains in samples from different geographic regions. Analysis of all US samples indicates high prevalence of APPV in Minnesota (37.35%), followed by Illinois (32.86%), Iowa (30.60%) and Kansas (21.89%). APPV was detected in 15.48% of samples assayed from 2017, slightly higher than that in 2016 (13.08%), but much lower than 2018 (28.77%). Among the various sample types tested, oral fluid samples had the highest prevalence and lowest average Ct value suggesting their suitability as a reliable diagnostic specimen for APPV detection. Overall, sequence variation among APPV strains and prevalence of the pathogen within the United States provides a basis for understanding the genetic diversity and molecular epidemiology of APPV in the US swine herds.

A Novel Real-Time PCR Assay for the Rapid Detection of Virulent Streptococcus equi Subspecies zooepidemicus—An Emerging Pathogen of Swine

Streptococcus equi subspecies zooepidemicus, a zoonotic bacterial pathogen caused a series of outbreaks with high mortality affecting swine herds in multiple locations of the USA and Canada in 2019. Further genetic analysis revealed that this agent clustered with ATCC 35246, a S. zooepidemicus strain associated with high mortality outbreaks in swine herds of China originally reported in 1977. Rapid and accurate diagnosis is absolutely critical for controlling and limiting further spread of this emerging disease of swine. Currently available diagnostic methods including bacteriological examination and PCR assays do not distinguish between the virulent strains and avirulent commensal strains of S. zooepidemicus, which is critical given that this pathogen is a normal inhabitant of the swine respiratory tract. Based on comparative analyses of whole genome sequences of the virulent isolates and avirulent sequences, we identified a region in the SzM gene that is highly conserved and restricted to virulent S. zooepidemicus strains. We developed and validated a novel probe-based real-time PCR targeting the conserved region of SzM. The assay was highly sensitive and specific to the virulent swine isolates of Streptococcus equi subspecies zooepidemicus. No cross reactivity was observed with avirulent S. zooepidemicus isolates as well as other streptococcal species and a panel of porcine respiratory bacterial and viral pathogens. The PCR efficiency of the assay was 96.64 % and was able to detect as little as 20 fg of the bacterial DNA. We then validated the diagnostic sensitivity and specificity of the new PCR assay using a panel of clinical samples (n = 57) and found that the assay has 100% sensitivity and specificity as compared to bacteriological culture method. In summary, the PCR assay will be an extremely valuable tool for the rapid accurate detection of virulent swine S. zooepidemicus isolates and directly from clinical samples.

Assessment of Soy-Based Imports into the US and Associated Foreign Animal Disease Status

Soy-based products are known to pose a viable risk to US swine herds because of their ability to harbor and transmit virus. This study evaluated soy imports into the US as a whole and from foreign animal disease positive (FAD+) countries to determine which products are being imported in the highest quantities and observe potential trends in imports from FAD+ countries. Import data were accessed through the United States International Trade Commission website (USITC DataWeb) and summarized using R (version 4.0.2, R core team, Vienna, Austria). Twenty-one different Harmonized Tariff Schedule (HTS) codes were queried to determine quantities (US tons, T) and breakdown of different soy product types being imported into the US from 2015 to 2020. A total of 78 different countries exported soy products to the US in 2019 and 2020, with top contributors being Canada (602,377 T and 530,759 T, respectively), India (438,563 T and 474,678 T, respectively), and Argentina (134,610 T and 87,602 T, respectively). In 2020, soy oilcake (641,846 T) was imported in the largest quantities, followed by organic soybeans (297,838 T) and soy oil (148,190 T). Of the 78 countries, 46 had cases of FAD reported through the World Organization for Animal Health (OIE) World Animal Health Information Database (WAHIS). Top exporters of soy products to the US from FAD+ countries in 2019 and 2020 were India (438,563 T and 474,678 T, respectively), Argentina (134,610 T in 2019), and Ukraine (44,415 T and 62,162 T, respectively). A system to monitor the sourcing of these products into the US and the end usage would allow for a greater understanding of the risk of these products to domestic swine herds.